Telephone system



Aug. 8, 1944.' J. G. WALSH TELEPHONE SYSTEM Filed nep. 15,; 1942 3Sheets-Sheet l [III A7' TORNE V Aug. 8, 1944. J, G, WALSH i l 2,355,251

TELEPHONE SYSTEM Filed Dec. 15, 1942 3 Sheets-Sheet 2 co/v/vEc ronNVE/ENTOR J a. WALSH By KCW@ Aug. s, 1944. J, G. WALSH 2,355,251v vTELEPHONE SYSTEM Filed Dec. 15, 1942 s sheets-sheet s FVG 4 CMM ATTORNEYPatented Aug. 8, 1944 TELEPHONE SYSTEM John G. Walsh, Newark, N. J.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application December 15, 1942, Serial No.469,090

6 Claims.

This invention relates to telephone systems and particularlyto systemsarranged for a plurality of classes of service including message rateservice.

Objects of the invention are an increase in the efliciency and adecrease in the cost of telephone systems arranged for a plurality ofclasses of service including message rate service.

It is known in automatic telephone systems to provide a trunk circuitindividual to the iii-st selector employed in establishing connectionsfrom calling message rate lines for controlling the operation of thecalling subscribers register. It is also known to provide means inautomatic telephone systems effective to transmit a classof-serviceindication to the answering operator on special service or interceptedcalls. In some arrangements the lines of each class are grouped in thebanks of` line-nder switches, the transmission of the class-of-serviceindication being eiected by actuation of normal post springs on thelevel or levels in which the lines of a particular class are terminated.

This invention is an automatic telephone system in which the linecircuit of a subscribers line includes an additional conductor forindicating the class of service to which the subscriber is entitled soas to allow connection of the line to any set of terminals in the banksof lineiinder switches, and in which the operation of a message ratesubscribers meter is controlled over the line conductor which is used togive the classof-service indication. 1= According to another feature ofthe invention, the line circuit of a message rate subscribers lineincludes an additional conductor for controlling the operation of thesubscribers message register instead of effecting the operation of Atheregister by the connection of a booster battery potential to the sleeveconductor used for operating the line cut-off relay thereby to obviatethe necessity of providing a booster battery, the additional conductorbeing further utilized to give a classof-service indication so as toallow connection of afmessage rate line to any set of terminals in thebanks of the line-finder switches.

A system embodying the invention and its features is representedschematically in the drawings which form apart of this specication. Theinvention is not limited to the specic system shown in the drawings butis generally applicable to automatic telephone systems.

Referring to the drawings:

Fig. 1 shows a subscribers station A and line LI, a line circuit LCI, aline `finder LFI, a connector CI, a message rate trunk circuit MRT, anda rst selector SI Fig. 2 shows a connector C2, a line L2 and asubscribers station B;

Fig. 3 shows a trunk circuit TCI connecting a set of terminals in thebank of the selector SI of Fig, 1 to a trunk T; and

Fig. 4 shows a trunk circuit TG2 connecting the trunk T to a jack at anoperators position.

Each of the subscriber-s stations A and B is of the usual type employedin common battery systems and includes a dial or other impulse sendingdevice for controlling the operation of switches to establish desiredconnections. The line finders LFI, selectors SI and connectors C! and C2are of the well-known two-motion stepby-step type. The line finder LFI,selector SI, and connectors CI and C2 are each represented by a set of`brushes and one or two sets of terminals. Reference may be had t0 pages53 to 65, inclusive, of the second edition-of Automatic Telephony" bySmith and Campbell for a description of the structure of such switchesand their operation when used as selectors and connectors. Reference maybe had to the patent to T. L. Dimond No. 2,210,068, granted August 6,1940, for a description of the operation of a twomotion step-by-stepline-nnder switch.

Assume now that a call is initiated at station A, the line relay I ofline circuit LCI being energized in series with the conductors of lineLI to actuate its outer frontcontacts, thereby con.- necting ground toconductor I'I to start an idle line nder and connecting the middlewinding of -relay I0, through conductor I3, to the test terminals of theline circuit LCI in the banks of a group of line lindern including thefinder LFi. Assuming the iinder LFI to be the nder which `is operated,the middle winding of relay IB is energized to fully operate relay I0when the test brush 23 engages the terminal to which conductor I3 isconnected and the line nder is stopped with its brushes 2|, 22, 23 and2.4 in engagement with the terminals to which conductors II, I2, I3 andI4 of line circuit LCI are connected. As soon as the eut-through relay(not shown) of line inder LFI is operated, as Vdescribed in vtheaforementioned patent to T. L. Dimond, the line LI is connected throughconductors II and -I2, brushes 2l and 22, and the windings ofsupervisory relay 3U of message rate trunk circuit MRT to the line relay(not show-n) of selector SI. Holding ground potential is thereuponconnected to sleeve conductor 2l in usual manner -to hold the line nderLFI in operated position and to maintain the operative energizationofthe middle winding of relay I. The complete operation of relay Idisconnects the conductors o line LI from the outer windings of relayIii and disconnects ground from start conductor I1. Relay 39 ispolarized and the current through its windings is ineffective to causeits operation at this time. If the calling line is a message rate line,a register I is connected to the terminal engaged by brush 24; if thecalling line is one of a second class of lines, ground is connectedthrough a resistor I6 to the terminal engaged by brush 24 as shown inFig. 1A; or if the calling line is one of a third class there is noconnection to the terminal engaged by brush 24. 'If the calling line isa message rate line, the winding of class-of-service relay 25 isconnected through conductor 2D, brush 211 and conductor i in seriesYwith register I5; and relay 25 is thereby iully energized to actuate allof its contacts, but register I5 is marginal and does not operate atthis time. If the calling line is one having a resistor I6 connected tothe terminal engaged by brush 24, relay 25 is only partially energized;and, if the calling line is one of the third class, relay 25 remainsnormal. lf relay 25 is operated completely, it locks through conductor21 to holding ground potential in the selector SI, connects -ground toconductor 29, and connects grounded conductor 21 directly to conductor28; if relay 25 is operated only partially, grounded conductor 21 isconnected to conductor 28 through resistor 26; and if relay 25 remainsnormal, there is no connection oi ground potential to conductor 2S.

When the calling line is connected to selector SI, dial tone istransmitted to the calling station A, in usual manner, to indicate thatthe subscriber may start dialing, When the calling subscriber dials therst digit, the brushes of selector SI are stepped up to the levelcorresponding to the digit dialed and the brushes are thereupon advancedstep by step to select an unguarded set of terminals in the selectedlevel. Assuming this call to be one for another subscriber inthe samedial oliice, the selected set of terminals 4U is connected throughconductors 4I, 42 and 43 to an intermediate selector (none shown) ordirectly to a connector C2, as shown in the drawings.' Upon extension ofthe connection to a connector C2, the line relay E5 is operated inseries with the calling line LI. Relay 45 closes a circuit for operatingslow-torelease relay 4; relay Iii connects holding ground potential,through conductor 63, to the -terminal engaged by brush 31 to hold theselector SI, to hold relay 25 if operated, to hold the line nder LFI,and to maintain the energization of the middle winding of relay I0.Relay d5 responds to the trains of impulses created by the dialing ofthe line selecting digits of the called subscribers number, therebyeiecting the operation of the connector to establish conection with thecalled line L2. The called line is tested and, if idle, the ringer atthe called station B is operated. All of these operations are eiiectedin usual and well-known manner. When the call is answered, relay 46 isoperated thereby interchanging the connections between the windings ofrelay 45 and conductors @I and 42 vso as to reverse4 the direction ofthe current through the windings of supervisory relay 39 of trunkcircuit MRT and thereby cause the operation of relay 39. AIf the callingline is a line other than a message rate line and relay 25 is notcompletely operated, the operation of relay 39 is without eiect. But, ifthe calling line is a message rate line so that relay 25 is fullyoperated, a circuit for energizing the upper winding of relay 3| isclosed when relay 30 operates or as soon thereafter as ground is nextconnected to conductor 29 by the interrupter which is common to all ofthe message rate trunk circuits. The interrupter intermittently connectsground to conductor 29, for instance for onehalf a second out of everytwo and a half seconds. The energization of the upper winding of relay3i effects the actuation of its outer lower front contact withoutactuating its other contacts. The lower winding of relay 3I is therebyconnected to conductor 21 in series with the upper winding but, as longas ground is connected to conductor 29, the lower winding of relay 3I isshort-circuited. AS soon after relay 3l is partially operated as groundis disconnected from conductor 29, both windings of relay 3| areenergized in series and the complete operation of this relay is therebyeffected. At its outer upper front contact, relay SI connects thewinding of relay 32 to conductor 29; and, as soon as ground is nextconnected to conductor 29, relay 32 operates. Relay 32 locks directly togrounded conductor 21, disconnects ground from conductor 20, connectsbattery through resistance 33 to conductor 20 to operate the marginalregister I5 of the calling line, disconnects the windings of relay 3lfrom conductor 21 and connects these windings to conductor 29. Relay 3lis thereby held operated until ground is next disconnected fromconductor 29. When relay 3l releases, battery is disconnected fromconductor 2G to release the register I5 and ground is reconnected toconductor 20. The connection between stations A and B is maintaineduntil the telephone set is restored to normal at station A, whereuponrelay 45 is released; and so also is relay 39, if operated. The releaseof relay causes the release of relay 44. Relay 44 disconnects groundfrom conductor 43, thereby effecting the release of the selector SI, therelease of relays 25 and 32, if operated, the release of line nder LFIand the release of relay I0. If the telephone at station B is alsorestored to normal, the connector C2 returns to normal in usual manner.f

Assume neXt that the subscriber at station A initiates a call to anoperator, in which case the dialing of the digit 0 (or any other digitwhich is used as the code for calling an operator) causes the selectorSI to select a set of terminals 50 in the corresponding level of itsbank, which set of terminals is connected to an idle trunk circuit TCIassociated with a trunk T leading to an operators position. When thecut-through relay (not shown) of selector SI operates, the connectionfrom the calling line is extended through brushes 35, 36, 31 and-38 totrunk circuit TCI, thereby efecting the operation of line relay 89. Thecircuit for operating relay 89 is traced from battery through the rightwinding of relay B9, inner upper back contact of relay 81, upper leftwinding of repeating coil RCI, another back contact of relay 81,conductor 52, brush 36 of selector SI, lower winding of relay 39, brush22 of line finder LFI, conductor I2 of line LI, through the telephoneset at station A, conductor II of line LI, brush 2I of line iinder LFI,upper winding of relay 30, brush 35 of selector SI, conductor 5I, a backcontact of relay 81, lower left winding of repeating coil RCI, innerlower back contact of relay 81, and the left winding of relay 89 toground. Relay 30 does not operate since the current through its Windingsis in the non-operate direction. Relay 89 closes circuits for operatingrelays 84 and 90.`

Relay 84 connects ground to conductor 53 to guard against seizure oftrunk circuit TCI by any other selector, to hold selector SI and lineinder LFI, to hold relay 25, if operated, and to hold relay I operated.Relay 84 also closes a connection between condenser 9| and conductor 52for transmitting ringing tone to the calling subscriber to indicate thatan operator is being signaled. Relay 90 interchanges the connectionsbetween the windings of relay 86 and conductors 9'! and 98 of trunk Tleading to an operators position thereby effecting the operativeenergization of both windings of polarized relay |00 of trunk circuitTG2 at the distantend of trunk T. Although the windings of relays 86 and|00 arev connected in a normally closed circuit over trunk T, thecurrent is not strong enough to operate the marginal relay 8G and is inthe non-operating direction with respect to relay |00, The operation ofrelay |00 closes a circuit for operating relay I 0I; relay I 0I closes acircuit for operating relay |02; and relay |02 closes a circuit foroperating relay I 03. Relay |0| also closes a circuit for lightinganswering lamp `I I3. Relay |03 closes a circuit for lighting busy lampIId and connects a busy potential, through resistor H8 and the lowerwinding of relay |05, to the sleeve of jack IIZ.

lf the call is from a message rate line, relay ,83 is fully operated dueto the complete operation of relay 25 as hereinbe'fore described. Ifrelay 25 is only partially operated, resistor 2S limits the currentthrough conductors 28 and 54 to only partially operate relay 83; and, ifrelay 25 is not operated, relay 83 remains normal. With relay 83completely operated, tone source T2 is connected to condenser T; andwith relay 83 only partially operated, tone source TI is connected `,tocondenser T. With relay $33V either partially or fully operated, acircuit is closed for operating slow-to-release relay 82.

When an operator answers the call by inserting the plug of a cord injack II2, a circuit is closed from battery in the operators positioncircuit through the sleeve conductor of the answering cord and jack I I2and the upper winding of relay |05. Reference may be had to Patent No.2,209,777 granted to R. E. King et al. July 30, 1940, for a disclosureof cord and position circuits arranged for cooperation with the trunkcircuit TG2. Relay |05 operates, closing a circuit for operating relay|03. Relay |06 closes a circuit for operating relay |01; closes ashort-circuit around the high resistance, upper winding of relay |00,thereby causing the operation of relay 86 of trunk circuit TCI; andopens the circuit through the winding of relay IOI to release this relayand extinguish lamp II3. Relay |01 closes a holding circuit for relay|02 and completes a talking connection between the right windings ofrepeating coil RC2 and the line conductors of jack II2.

The aforementioned operation of marginal relay 88, when the call isanswered, closes a circuit for operating relay 80. Relay 00 disconnectscondenser 9| from conductor 52, to end the transmission of ringing toneto the calling subscriber, and causes the release of relay 82.

While relay 82 is releasing, a class-of-service tone is transmittedthrough condenser T and front contact of relay 82 to conductor 52,thence through repeating coils RCI and RC2 to the answering operator toindicate the class of the calling subscriber. If relay 83 is operatedcompletely, the tone is from source T2; if relay 83 is .partiallyoperated, the tone is from source TI; and if relay 8,3 is normal, notone is `transmitted.

VThe talking connection between the station A and operator includesrepeating coils RCI and RC2 and the connection is under the jointcontrol of the calling subscriber .and answering operator. When thetelephone at station A is restored to normal, relay 89 releases vtherebycausing` the release of relay 90 so as to restore the current over trunkT to its normal direction and thus effect the release of relay |00 oftrunk cir- `cuit TC2. When relay |00 releases, it connects ground to thelower, low resistance winding of relay |05 thereby causing the lightingof a supervisory lamp in the operators cord circuit as a disconnectsignal. When the operator disconnects, relay |05 releases causing thesuccessive release of relays |06 and I0'I. Relay I0IV reoperates ifrelay |00 has not released. The release of relay |05 opens theshort-circuit around the upper, high resistance winding of relay |00thereby causing the release of relay of trunk circuit TCI. release ofrelay 80. When both the calling subscriber and answering operator havereleased the connection, relay 84 releases, thereby disconnecting groundpotential from conductor 53 to effect the release of selector SI, linefinder LFI and relay I0.

What is claimed is:

l. In a telephone system, subscribers lines including message ratelines, means including a trunk circuit interconnecting a callingYmessage rate line and a called line, said trunk circuit comprising aclass-o-service relay, a message register for said calling line, theconnection between the calling line and trunk circuit comprising aconductor interconnecting said message register and said class-of-service relay thereby to operate said relay, said register beingmarginal to prevent its operation in series with said relay, and meansincluding contacts of said relay for operating said register responsiveto the answering oi the call at the subscribers station on the calledline. v

2. In a telephone system, subscribers lines including message ratelines, a message register for each of said message rate lines, a trunkcircuit, means responsive to the initiation of a call on one of saidlines for connecting the calling line to said trunk circuit, anoperators position, means including subscriber controlled switchingmeans for selectively connecting said trunk circuit with alcalledsubscribers line or with said operators position, relay means in saidtrunk circuit,` means comprising the message register of a callingmessage rate line connected to said trunk circuit for selectivelyoperating said relay means to indicate that the calling line is amessage rate line, means comprising means individual to a line, otherthan a message rate line, connected to said trunk circuit forselectively operating said relay means to indicate that the calling lineisnot a message rate line, and means including said relay means in saidtrunk circuit for effecting the operation of the message register of acalling message rate line connected to said trunk-circuit in response tothe answer of a call to one of said subscribers lines.

3. In a telephone system, subscribers lines in- The release of relay 86causes the cluding message rate lines, a message register for each ofsaid message rate lines, a trunk circuit, means responsive to theinitiation of a call on one of said `lines for connecting the callingvline to said trunk circuit, an operator-s position, means includingsubscriber controlled switching means for selectively connecting saidtrunk circuit with a called subscribers line `or withsaid operatorsposition, relay means in said trunk circuit, means comprising themessage register of a calling,r message rate line connected i toV saidtrunk Icircuit for selectively operating said relay means to indicatethat the calling line is a message rate line, means comprising meansindividual to a line, other than a message rate line, connected to saidtrunk circuit for selectively operating said relay means to indicatethat the calling line is notv a message rate line, means including saidrelay means in said trunk circuit for effecting the operation of themessage register of a calling message rate line connected to said trunkcircuit in response to the answer of ra call to one ol said subscriberslines, and means selectively controlled by said relay means in saidtrunk circuit on a call to said operators position for indicating to theanswering operator the character of the calling line.

V4. In a telephone system, subscribers lines of different classesincluding message rate lines, a message register for each of saidmessage rate lines, a trunk circuit, means responsive to the initiationof a call over one of said lines for connecting the calling line to saidtrunk circuit, class of -service relay means in said trunk circuit,means including the message register of a message rate line connected tosaid trunk circuit for selectively operating said class-of-service meansto indicate that the connected calling line is a message rate line,means including means individual to a line of another class connected tosaid trunk circuit for selectively operating said class-of-service meansto indicate that the call is from a line of said other class. anoperators position, switching means controlled by the calling subscriberover the calling line and said trunk circuit in series for completing aconnection with a. called subscribers line or with said operatorsposition as desired, means selectively operated under the control ofsaid class-of-service relay means in said trunk circuit for giving tothe answering operator on a call to said position an indication of theclass of the connected calling line, and register operating means insaid trunk circuit operatively responsive to the answer of a call thoughsaid trunk circuit to a called subscribers station, the selectiveoperation of said class-of-service relay means being effective toconnect said register operating means to the register of a callingmessage rate line.

- 5. In a telephone system, subscribers lines of a plurality of classes,the lines in one of said classes being message rate lines, a messageregister for each of said message rate lines, the winding of Yeach ofsaid registers having low electrical resistance, a resistor'individuaito each line in another of said classes, eachof said .resistors having asubstantially higher resistance than each of said registers, a trunkcircuit, means responsive to the initiation of a call over any one ofsaid lines for connecting the calling line to said trunk cir- Cil sagerate line, said connecting means comprising talking conductors, aholding conductor and a control conductor, said control conductorconnecting said class-of-service relay in series with the messageregister of a connected calling message rate line to fully operate saidclass-of-service relay in series with said register without operatingsaid register, saidcontrol conductor connecting said class-of-servicerelay in series with the individual resistor of a connected calling lineof said other class to partially operate said classoi`service relay, thepartial operation of said class-of-service relay being ineffective andthe complete operation of said class-of-service relay being eiective toclose a locking circuit, to clisconnect the relay from said controlconductor and to connect said control conductor to said relay means, andanswering supervisory means in said trunk circuit for operating saidrelay means thereby to eiTect the closing of a circuit through saidcontrol conductor for operating the message register of a connectedcalling message rate line.

6. In a telephone system, subscribers lines of a plurality of classes,the lines in one of said classes being message rate lines, a messageregister for each of said message rate lines, the winding of each ofsaid registers having low electrical resistance, a resistor individualto each line in another of said classes, each of said resistors having asubstantially higher resistance than each of said registers, a trunkcircuit, means responsive to the initiation of a call over any one ofsaid lines for connecting the calling line to said trunk circuit, saidtrunk circuit comprising a class-ofservice relay and relay means for usein operating the message register of a connected calling message rateline, said connecting means comprisn ing talking conductors, a holdingconductor and a control conductor, said control conductor connectingsaid classofservice relay in series with the message register of aconnected calling message rate line to fully operate saidclass-of-service relay in series with said register without operatingsaid register, said control conductor connecting said class-of-servicerelay in series with the individual resistor of a connected calling lineof said other class to partially operate said class-of-service relay,the partial operation of Asaid class-of-service relay being ineffectiveand the complete operation of said class-of-service relay being eiectiveto close a locking circuit, to disconnect the relay `from said controlconductor and to connect said .control conductor to said relay means, anoperators position, subscriber controlled switching means forestablishing connections between calling lines and called lines andbetween calling lines and said operators position, each of saidconnections including said trunk circuit,means selectively controlled bysaid classof-service relay for indicating to the answering operator theclass of the connected calling line on a call to said position, meansincluding a supervisory relay in said trunk circuit for operating saidrelay means responsive to answer of a cali to a called subscribers line,the complete operation of said class-of-service relay and theoperatlonof said relay means being effective to close a cir-cuit throughsaid control conductor for operating the message register of a connectedcalling message rate line.

J OHN G. WALSH.

